The present invention relates to orthodontic appliances and is specifically concerned with a new and improved orthodonic appliance for jaw correction.
An anatomical condition, namely mandibular retrognathia, has a significant incidence among orthodontic patients and involves deviation of the lower jaw position from the norm. This condition may be independent of dental malposition per se, and involves a disposition of the entire lower jaw which is considered to detract from an individual's appearance, and which may be a cuase of improper bite. Specifically the condition may comprise an individual's lower jaw being set posteriorly from what would be considered a more favorable location from the standpoint of appearance and/or bite.
An orthodontic appliance which has been available for correcting this condition in certain circumstances is known as the Herbst appliance. Briefly, the Herbst appliance comprises positioning structure which is operatively disposed between the upper and lower dental arches and which is effective, when applied to an individual over a course of time, for improving the aforementioned condition. Over the course of treatment, the positioning structure is effective to cause the lower jaw to naturally assume a more anterior placement by limiting the posterior displacement of the lower dental arch in relation to the upper dental arch. Other types of appliances have also been addressed to correcting the same problem.
The present invention, in one respect, is directed to an improvement in a Herbst type appliance. A Herbst appliance is limited in application because of the manner by which the positioning structure is operatively related to the respective dental arches. In particular the connections of the positioning structure to the dental arches involves the use of individual bands on individual teeth. Accordingly, the Herbst appliance has been suitable generally only for patients in late adolescence where all permanent teeth including the mandibular first bicuspids have erupted so as to provide adequate structure for the individual bands. The Herbst appliance has not been generally recognized as suitable for treating younger individuals for the reason that they lack a complete set of permanent teeth and therefore do not possess adequate dental structure for application of the appliance. Yet, a very effective treatment time for correcting the jaw is pre- and early adolescence.
The present invention constitutes an improvement over the Herbst appliance in that the appliance of the invention is suitable for application during this very effective pre- and early adolescent treatment time.
The invention provides an appliance suitable for use with individuals who do not possess a full set of permanent teeth, particularly children. It has the advantage of being easily applied to patients regardless of age, provided that at least a certain number of teeth are present, even though not a full set. The invention is also highly effective in that the manner by which the positioning structure is operatively related to a dental arch takes place with the arch being stabilized as a unit.
The possibility also exists in certain patients that attempted correction of the jaw through use of a Herbst appliance may give rise to other problems necessitating correction by way of other treatment procedures. For example, tooth separation and/or rotation may occur in response to usage of a Herbst appliance, due principally to the previously accepted manner of operatively relating the appliance to the individual teeth as explained above. Use of the Herbst appliance may result in permanent damage to the incisor teeth due to fracture. During operation of the appliance, the posterior teeth are disoccluded, and the entire biting force may be directed onto the incisor teeth. This can result in fracture if these teeth are brought together forcefully during biting.
Because the improved appliance of the present invention stabilizes the entire dental arch rather than being connected to two individual teeth of the arch, it can be applied with minimum liklihood that separation, rotation and/or fracture will occur. One portion of the improved appliance is effective to cushion the biting force on the incisor teeth and redistribute it over other teeth as well. In this way the possibility of fracture is significantly lessened. This one portion of the appliance also reacts the corrective forces in such a manner that both separation and/or rotation of individual teeth are much less likely than in the case of the Herbst appliance. The complementary portion of the improved appliance, through stabilization of its arch, is also less likely to cause separation and/or rotation. In addition to possessing these attributes the invention is also versatile enough to be used concurrently with other treatment procedures.
The present invention in its preferred embodiment comprises an acrylic plastic splint which is applied through a bonding agent to the cusps of the teeth of the lower dental arch. The plastic splint has a generally U-shaped configuration forming to the shape of the lower arch and can be readily fabricated in accordance with conventional fabrication techniques. Embedded within the plastic body of the splint, at each lateral side, is a metal insert. Each metal insert has perforations, and during fabrication of the splint the acrylic plastic cures onto the metal inserts with the plastic material filling the perforations so as to lock the inserts in place. The inserts are generally toward the posterior of the appliance, and the anterior portion of the splint preferably includes a reinforcing wire which bridges the span between the metal inserts. Projecting from each insert through the plastic is a pivot which provides a pivot connection to one element of the corresponding positioning structure. The positioning structure takes the form of telescopically engaged elements, with a rod element being pivoted on each pivot of the splint and a corresponding sleeve telescoping onto the rod element and operatively connected to the upper arch. Each rod element has an eyelet fitting onto the corresponding pivot. The end of each sleeve element abuts the corresponding eyelet to limit the rearward displacement of the lower arch in relation to the upper arch, thereby allowing anatomical forces to urge the lower jaw forwardly to the end that it will naturally assume a more anterior position. To assist the splint in reacting the forces and torques which are developed through use of the appliance, it is desirable to provide clasps at the posterior ends of the splint which can be engaged with brackets mounted on molar bands on the lower molars.
The appliance further includes connection of each sleeve element to the upper dental arch by mated connector structures connecting the sleeve to a molar band on an upper molar tooth. The mated connector structures comprise a bracket (double buccal tube) on the outside of the molar band and a fitting on the sleeve. The bracket comprises a pair of tubes, and the fitting comprises a pair of projections which fit into the bracket tubes. The sleeve also includes a pivot joint immediately adjacent the fitting. One projection of the fitting has a circular cross section which fits within a corresponding tube of similar circular cross section. The other tube and corresponding projection have polygonally shaped cross sections.
The foregoing features, advantages, and benefits of the invention, along with additional ones, will be seen in the ensuring description and claims which should be considered in conjunction with the accompanying drawings. The drawings disclose a preferred embodiment of the invention according to the best mode contemplated at the present time for carrying out the invention.